For my modeling I often have to solder brass parts and pieces together. For something complex I'm likely to make a jig to hold the pieces (which can be as small as 1/32" diameter by a few 32nds of an inch long). For a Q&D one-time jig, I often use balsa but have recently started to use scrap red oak because it's significantly harder and can take the heat better. But there are many times I feel that I really need a material with no grain to have to fight in cutting, chiseling, and drilling. Are there any plastics that can withstand the heat of a conventional soft-soldering operation, say300-475 F for short periods without distorting or giving off dangerous fumes?